Mixing and kneading device

ABSTRACT

A mixing and kneading device comprising a housing and a shaft mounted therein. The shaft carries a conveyor helix and mixing and kneading vanes. The vanes cooperate with stationary elements in the housing to carry out the kneading and mixing functions. The shaft is rotated by a variable speed rotary motor and is also reciprocated to move the vanes toward and away from the stationary elements by a pressure fluid motor having its piston connected to the shaft. The rate of reciprocations of the piston and shaft is cyclically controlled by a valve device which is actuated by a cam driven by a variable speed motor to thereby vary the number of reciprocations during a revolution of the shaft. A second valve device regulates the flow of pressure fluid during a cycle to reduce or stop the flow of fluid to the piston near the end of the shaft&#39;&#39;s stroke toward the stationary elements.

United States Patent [72] lnventors Fritz Ronner;

Fritz Sutter, both of Pratteln, Switzerland [21] Appl. No. 23,796 {22]Filed Mar. 30, 1970 [45] Patented Nov. 9, 1971 [73] Assignee Buss A. G.,Barfusserplatz Basel, Switzerland [32] Priorities Apr. 2, 1969 [3 3]Switzerland [31 5387/69;

Feb. 5, 1970, Switzerland, No. 1778/70 [54] MIXING AND KNEADING DEVlCE16 Claims, 6 Drawing Figs.

[52] 11.8. C1 259/102, 259/5, 259/21, 259/40, 15/7465 [51] 1nt.C1B01f7/00 [50] Field of Search 259/213, 4-9, 16, 21-26, 102. 32-35,40-45,64-70, 17, 27, 47,52, 59, 79,93, 1 12, 123, 111; 15/2465 [56] ReferencesCited UNlTED STATES PATENTS 2,801,237 7/1957 Clevy et a1. 259/93 X3,023,455 3/1962 Geier et a1. 259/9 X 3 (f8; I i Isl e I; i l I +l |l1 J3,047,907 8/1962 Hanusch et a1. 259/4 X 3,189,324 6/1965 Gubler 259/93,219,320 11/1965 Sutter 259/5 3,301,138 1/1967 Cox 259/10X 3,346,24210/1967 List 259/5 X 3,347,528 10/1967 List et al. 259/2 3,367,6352/1968 Gresch 259/4 2,505,125 4/1950 List 259/93 Primary Examiner-JordanFranklin Assistant E.raminer-George V. Larkin Attorney-Abraham A.Saffitz ABSTRACT: A mixing and kneading device comprising a housing anda shaft mounted therein. The shaft carries a con veyor helix and mixingand kneading vanes. The vanes cooperate with stationary elements in thehousing to carry out the kneading and mixing functions. The shaft isrotated by a variable speed rotary motor and is also reciprocated tomove the vanes toward and away from the stationary elements by apressure fluid motor having its piston connected to the shaft. The rateof reciprocations of the piston and shaft is cyclically controlled by avalve device which is actuated by a cam driven by a variable speed motorto thereby vary the number of reciprocations during a revolution of theshaft. A second valve device regulates the flow of pressure fluid duringa cycle to reduce or stop the flow of fluid to the piston near the endof the shafts stroke toward the stationary elements.

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sum u 0F 4 INVENTORS FRITZ RONNER FRITZ SUTTER ATTORNEY MIXING ANDKNEADING DEVICE Mixing and kneading devices are known in which thekneading member performs a synchronous to and fro movement which issuperimposed over the normal rotary movement. Thus, for each revolution,the kneading member moves between the most forward and the rearmostposition inside the kneader casing. The inside of the casing is providedwith fixed projections or toothlike kneading obstacles which, duringeach revolution, pass through appropriate interruptions of the flightsof the kneading member and strip off the kneaded material.

During the movement, a wedge-shaped space forms between the obstaclesand the flights of the rotating kneading member, and part of the kneadedmaterial is forced through this space. The mixing rate and kneadingintensity may be varied, depending upon the selected shape and size ofthe kneading member and of the obstacles. The dispersion and subdividingof the material in its flow influences the mixing and the ease ofpassage between kneading member flights and obstacles influenceskneading.

The simultaneous rotation and to and fro movement results in a combinedmovement in a form resembling a sine curve in which the materialthroughput varies in proportion to the revolutions of the shaft of thekneading member.

With known machines, the simultaneous movements are created in gearunits of special construction permitting only limited variations ofmixing and kneading intensity in relation to throughput. Walter GreschUS. Pat. No. 3,219,320, issued Nov. 23, 1965 and entitled, Method ofContinuous Kneading and Mixing, and an Arrangement for Carrying Out theMethod", uses a kneading member where the interruptions in the flightsare closed at appropriate positions with gap filling elements and, whenthe obstacles corresponding to the gaps are removed, the flow ofmaterial increases. In Danish Pat. No. 87,566, the arrangement of theinterrupted flight vanes provides inclined helicoidal lines whichproduce an increase in material throughput. This increase is enhancedwhen the vane edge is chamfered. A reduction of throughput at a givennumber of revolutions is obtained by increasing the shaft.

diameter of the kneading member as shown in FIG. 1 of US. Pat. No.3,189,324, issued to Ernst Gubler on June 15, 1965 and entitled,Kneading and Mixing Arrangement, or by using a baffle ring as disclosedin Walter Gresch US. Pat. No. 3,367,635, issued Feb. 6, 1968 andentitled, Arrangement for the Degasification of Plastic Masses DuringTheir Treatment by Means of a Continuous Mixing and Kneading Worm".

It is noteworthy that the known rotating and oscillating kneadingmachines using interrupted flights on the kneading member have a ratioof 1:1 between rotational movement and longitudinal reversing movement.

An object of this invention is to provide a simple mixing and kneadingdevice in which the ratio between throughout and mixing and kneadingefficiency can be adapted continuously over a wide range to make theprocess especially useful for chemical reactions.

In accordance with the present invention, there is provided a mixingdevice having a cylindrical casing forming a mixing chamber, with ashaft arranged therein, which carries out simultaneous rotating andoscillating movement, the shaft provided with vanelike mixing orkneading elements cooperating with obstacles mounted inside the casing.A single motor drive is provided for the rotational movement and anindependent driving means is provided for the oscillating movement, sothat the ratio of the rotary movement of the shaft to the reciprocatingmovement of he shaft can be varied in a continuous and advantageousmanner.

The chamfering of the edges of flight vanes which is employed in theprior art is of no practical benefit to increase throughput in thepresent device. With rapid rotary movement of the kneading shaft andslow reciprocating movement, there is created an advantageous type ofplug-flow and the plug which is formed of the material mixed within thecasing is subjected to a predetermined dwell time and throughput.

By changing the number of reciprocating movements per period and byvarying the speeds of the to and fro movements, and by using a differentspeed for the forward and backward strokes, a stepless adjustment forthe desired throughput can be achieved in a new manner. Thus, the mixingand kneading effect can be varied by changing the revolutions and issubstantially independent of the reciprocating movement.

A device according to the invention can be used advantageously in mayfields where continuous processing is required for simultaneous mixingand kneading; for example, chemical reaction, polymerization, drying,heating or cooling, and countercurrent extractions.

Two embodiments of the present device, one for mixing and kneading andthe other for continuous drying, are illustrated in the attacheddrawings in which:

FIG. 1 shows a section of a mixing and kneading device of the inventionin which the driving means is not shown;

FIG. 2 is a showing of the development of the kneading shaft of FIG. 1which includes in dotted lines with arrows the combined reciprocatingand rotational movements;

FIG. 3 is a vertical section illustrating the independent drivingarrangements for the rotary movement and for the reciprocating movementof the device of FIG. 1;

FIG. 4 is a vertical section of the mixing chamber of FIG. 1illustrating the vacuum flange attachment for vacuum mixing andkneading;

FIG. 5 illustrates an embodiment of the invention useful for drying,heating and cooling or for solvent extraction, the driving means beingomitted; and,

FIG. 6 is a sectional view on section line AA of FIG. 5.

The mixing and kneading device shown in FIG. 1 has a cylindrical casing1 provided with a feed hopper inlet 2 for solids and an inlet 3 forliquids, pastes or fluidized powders, the casing being subdivided into amixing chamber 9 at the feeding section and a kneading section 13between the inlet and the outlet. An outlet 4 is provided at theopposite end of the casing at the point most remote from the inlets 2and 3. Stationary kneading elements 5 are provided in the mixing chamber9 of the casing and serve as obstacles for the material flow. Theseelements 5 can be inserted into the casing and fixedly secured to thecasing from the outside. It is contemplated that the kneading elementsmay be fashioned with bores which serve as feeding tubes through whichadditional substances can be introduced into the mixing chamber.

A kneading shaft 6 is provided along the central longitudinal axis ofthe casing and is supported by main bearing 7 on the end of theshaftattached to the driving means. Additional bearing supports may beprovided in the casing.

The shaft 6 is provided with closed screw flights 8 in the feedingsection below feed inlet 2 to permit smooth, continuous delivery ofmaterial from the hopper to the mixing chamber 9. The screw flights 8serve the function of a conveyor helix on the shaft near the inlet. Theshaft 6 is also provided with mixing and kneading vanes 10 which arespaced longitudinally along the shaft in the feeding and kneadingsections. Kneading elements 5 are inserted in a staggered helicoidalpattern within the casing l downstream of the conveyor helix near theinlet. The material is mixed and kneaded very intensely within thefeeding section of the mixing chamber in advance of baffle ring 11inserted in the casing I. The worked material is pushed over this bafflering into the kneading section 13 of the mixing chamber which isprovided with an exhaust opening 14 to permit the withdrawal ofvolatiles in this zone which is used for degassing. The baffle ring islocated within the housing between the mixing and kneading vanes todivide the housing into a mixing section and a degassing section.

The opening 14 is covered by an observation window 20 and has a flangefor connection to a vacuum (shown in FIG. 4). Gap closing elements 15are inserted between consecutive vanes 10 on the kneading shaft 6 nearthe outlet end of the mixing chamber. These gap closing elements serveas mechanical stops to prevent backflow of the material near the outletdie 4 from interfering with the material flowing through the degassingzone.

As shown in FIG. 1, the entire kneading shaft 6 is hollow and isprovided along its length with concentric heating or cooling tubes whichpass in a heating or cooling medium at 16 and withdraw the medium at 17.In addition, liquid inlet 3 is supplied by line 19 with predeterminedportions of liquid from proportioning pump 18.

FIG. 2 is a view of the development of the screw flights 8 and the vanes10 on the kneading shaft 6 and the three different positions, a, b c,and c, of fixed kneading elements 5 are shown in dottedlines and arrowsin relation to the rotating kneading shaft. These positions, a, and c,result from three different ratios of rotation and reciprocatingmovement. Dotted line a results when one longitudinal forward and backstroke is synchronized with one revolution of the shaft 6. Dotted line bshows a double stroke per shaft revolution. Dotted line 0 shows a doublestroke for each shaft revolution and a stroke interruption occurring atthe end points for a duration corresponding to of revolution. The dottedlines illustrate regulation of periodically repeated wiping-offoperations at the kneading vanes over their entire width.

FIG. 3 schematically shows the combined drive for the shaft 6 which isconnected to hollow driving shaft 21 in line therewith. The drivingshaft 21 is guided in slide bearings and is driven through gear train23, 24 by variable speed motor 22. The end of the hollow driving shaft21 is provided with inlet 25 and outlet 26 for heating or coolingmedium.

The reciprocating movement is provided by a separate drive which ispowered by a variable speed motor 27. Keyed on the output shaft 28 ofmotor 27 is cam disc 29. The cam disc can be replaced to provide adifferent curve. The curve of the cam disc governs the rapidity of theforward stroke and the slowness of the backward stroke. Variations inthese rates are achieved by substituting discs. The curved surface ofthe disc 29 guides the spring loaded head 30 of hydraulic regulatingvalve 32. The regulating hydraulic valve 32 is a multiple-disc typefitted with cylinder 31, fed with fluid from pressure pump 33, anddriven by pump motor 27 whose transmission is not shown. The hydraulicpassageways in the regulating valve 32 lead to working cylinder 34mounted coaxially with hollow driving shaft 21, with working piston 35interposed therebetween. The piston 35 is clamped to the shaft 21 overball bearings 37 in such manner that the driving shaft 21 rotatesfreely, but the piston does not rotate, the ball bearings restingagainst the face of the tightening nut 36 which is threaded onto thedriving shaft 21.

Depending upon the position of disc 29, the hydraulic fluid flows underpressure either through line 38 or line 39 which pushes the pistoneither to the left or to the right. The movement in the forwarddirection to the right is assisted and the movement to the left isdampened by spring 40 mounted on nonturning piston 35.

The reciprocating movement to and at the turning point is controlled bya limit sensor having a bar transmission 41, the bar being pivoted onbearing point 43 and connected to the stem of sliding discs inside ofthe hollow stem of valve 32. These sliding discs provide a superimposedbypass for the hydraulic fluid within the valve 32 and serve to maintainthe hydraulic pressure at a desired value once the end position has beenreached and until the curve on cam disc 29 causes the stem 30 toreverse. The cam disc is curved to provide a holding position over 15 ofare at the periphery of the disc; and, in this 15 arc, the reciprocatingpush-pull motion is stopped. the hydraulic drive is assisted by thespring 40 which accumulates force during the backward stroke and expendsthis force to assist the forward stroke.

FIGS. 5 and 6 show an alternative embodiment for drying, heating orcooling, or solvent extraction in which the mixing and kneading devicehas a cylindrical casing 102 fed through hopper inlet 103 and exhaustedat outlet 104. The casing 102 is provided with shaft 105 mounted forrotating and reciprocating movement, the shaft being provided with pairsof mixing and kneading blades 106 mounted in diametric opposition. Theblades 106 scrape the inside walls of the casing and, in turn, are wipedby fixed scraping elements 107 which are inserted into the casing.

As shown in FIG. 6, the scraping elements 107 are located in the upperright in the casing when the shaft turns clockwise. The vacuum exhaustflange 108 is mounted on the casing near the discharge outlet 104 (FIG.5). Shaft is rigidly secured to the driving shaft 111, supported on thebearings 112, by a flange connection. The combined rotating andreciprocating drive for shaft 1 11 is furnished by a variable speedmotor in a case 109 which rests on pivotable support 110 on the samebase plate 101 which supports the casing. This mounting permits properalignment of the casing and motor during the reciprocating movement ofshaft 111.

The push-pull movements of shaft 111 are controlled by piston 113, therod 116 for the piston being keyed onto the end of the shaft 111 and thepiston sliding in a rigidly mounted cylinder 114. The velocity of thestroke may be regulated in the manner already illustrated and describedin connection with FIGS. l-4. The shafts 111 and 105 are hollow topermit circulation of a heating or cooling medium, and casing 102 isjacketed to permit heating or cooling.

When casing 102 is filled only up to 65 percent volume during operation,to the level shown in dotted line 118 in FIG. 6, the free space 119 canbe used for evaporative drying.

Dwell time and throughput can be readily varied by changing the ratio ofrotational to reciprocating movement. If the forward stroke is adjustedto occur with both blades in horizontal position, then both blades pushthe material forward. If the back stroke occurs with one blade in thefilled position and one blade in the free space 119 (FIG. 6) in verticalposition, then the backstroke will agitate only 50 to 55 percent of thematerial which was previously pushed forward. This permits a continuousor stepless adjustment between the horizontal and vertical positions,and the velocities of the forward and back strokes and of rotation mayall be adjusted independently.

What is claimed is:

l. a mixing and kneading device comprising a housing having an inlet anddischarge, a shaft mounted for rotation and reciprocation in saidhousing, spaced mixing and kneading vanes secured to said shaft,stationary kneading elements secured to the casing wall and cooperatingwith said vanes in the mixing and kneading functions, rotary means torotate said shaft, reciprocating means to cyclically reciprocate saidshaft to move said vanes toward and away from their cooperatingstationary elements, means to control the speed of rotation and means tocontrol the reciprocating means to vary the to and fro movement of saidreciprocating means using different speeds for the forward and backwardstroke.

2. A mixing and kneading device as set forth in claim 1, wherein theshaft is provided with a conveyor helix thereon near the inlet, saidmixing and kneading vanes being helicoidally arranged on said shaftdownstream of the helix, and wherein a baffle is located within thehousing intermediate the vanes to divide said housing into a mixingsection and a degassing section.

3. A mixing and kneading device as set forth in claim 2, wherein saidshaft carries a baffle member to define the end of the degassingsection, said baffle member being secured to the shaft between vanemembers near the discharge.

4. A mixing and kneading device as set forth in claim 2, wherein therotary means is a variable speed motor and a gear train operativelyconnecting said motor to said shaft.

5. A mixing and kneading device as set forth in claim 4, wherein saidreciprocating means is a pressure fluid motor comprising a relativelymovable piston, a hollow piston rod, a valve stem and a cylinder, saidrod being operatively connected to said shaft.

6. A mixing and kneading device as set forth in claim 5, wherein saidhollow piston rod is connected to said piston, said shaft passingthrough said hollow piston rod for free rotary movement therein, and camdisc connecting means for securing said piston to said shaft in abuttingrelation therewith to transmit the reciprocating movement of the pistonto the rotating shaft.

7. A mixing and kneading device as set forth in claim 6, wherein abiasing spring is provided on said valve stem to act upon the piston tobias it into the final position of a stroke in one direction.

8. A mixing and kneading device as set forth in claim 5, wherein thereciprocations of the pressure fluid motor are controlled by a fluiddistributing valve device connected thereto and wherein said valvedevice is cyclically actuated by a variable speed motor driven means.

9. A mixing and kneading device as set forth in claim 8, wherein saidvariable speed motor driven means comprises a variable speed motor, cammeans rotated by said motor, and means operatively connecting said cammeans to said valve device.

10. A mixing and kneading device as set forth in claim 9, wherein saidvalve device comprises a valve casing, supply, exhaust and motor portsin said valve casing, a slidable, hollow piston type valve member havingflow passages therein in said casing for selectively interconnectingsaid supply and exhaust ports to said motor ports to supply and exhaustpressure fluid to and from said cylinder.

1 1. A mixing and kneading device as set forth in claim 10, a flowregulating valve member located within said hollow valve member tocooperate with said flow passages to control the flow of fluidtherethrough, and means responsive to the reciprocatory movements ofsaid shaft to actuate said regulating valve to a position wherein itcooperates with said flow passages to regulate the flow of pressurefluid therethrough, said means responsive to the reciprocatory movementspositioning said regulating valve in its flow regulating positions atthe end positions of the shaft strokes.

12. A mixing and kneading device as set forth in claim 1, wherein thevanes are secured to the shaft in diametrically opposed pairs for anadditional wall scraping function, and cooperate with theircorresponding stationary elements.

13. A mixing and kneading device as set forth in claim 1, wherein saidhousing is provided with a connection adapted to be connected to avacuum means.

14. A mixing and kneading device as set forth in claim 1, wherein thereciprocating means is a stationary pressure fluid motor comprisingrelatively movable piston and cylinder elements with one of the elementsconnected to said shaft, and wherein the rotary means comprises avariable speed motor mounted upon said shaft for movement therewith.

15. A mixing and kneading device as set forth in claim 14, wherein saidrotary means is housed in a case, said case being mounted on a pivotablesupport.

16. A mixing and kneading device as claimed in claim 15, wherein saidpressure fluid motor is in axial alignment with the end of said shaftand said variable speedrotary motor is connected to said shaft by gearmeans concentric with said shaft.

l i i I! t

1. A mixing and kneading device comprising a housing having an inlet anddischarge, a shaft mounted for rotation and reciprocation in saidhousing, spaced mixing and kneading vanes secured to said shaft,stationary kneading elements secured to the casing wall and cooperatingwith said vanes in the mixing and kneading functions, rotary means torotate said shaft, reciprocating means to cyclically reciprocate saidshaft to move said vanes toward and away from their cooperatingstationary elements, means to control the speed of rotation and means tocontrol the reciprocating means to vary the to and fro movement of saidreciprocating means using different speeds for the forward and backwardstroke.
 2. A mixing and kneading device as set forth in claim 1, whereinthe shaft is provided with a conveyor helix thereon near the inlet, saidmixing and kneading vanes being helicoidally arranged on said shaftdownstream of the helix, and wherein a baffle is located within thehousing intermediate the vanes to divide said housing into a mixingsection and a degassing section.
 3. A mixing and kneading device as setforth in claim 2, wherein said shaft carries a baffle member to definethe end of the degassing section, said baffle member being secured tothe shaft between vane members near the discharge.
 4. A mixing andkneading device as set forth in claim 2, wherein the rotary means is avariable speed motor and a gear train operatively connecting said motorto said shaft.
 5. A mixing and kneading device as set forth in claim 4,wherein said reciprocating means is a pressure fluid motor comprising arelatively movable piston, a hollow piston rod, a valve stem and acylinder, said rod being operatively connected to said shaft.
 6. Amixing and kneading device as set forth in claim 5, wherein said hollowpiston rod is connected to said piston, said shaft passing through saidhollow piston rod for free rotary movement therein, and cam discconnecting means for securing said piston to said shaft in abuttingrelation therewith to transmit the reciprocating movement of the pistonto the rotating shaft.
 7. A mixing and kneading device as set forth inclaim 6, wherein a biasing spring is provided on said valve stem to actupon the piston to bias it into the final position of a stroke in onedirection.
 8. A mixing and kneading device as set forth in claim 5,wherein the reciprocations of the pressure fluid motor are controlled bya fluid distributing valve device connected thereto and wherein saidvalve device is cyclically actuated by a variable speed motor drivenmeans.
 9. A mixing and kneading device as set forth in claim 8, whereinsaid variable speed motor driven means comprises a variable speed motor,cam means rotated by said motor, and means operatively connecting saidcam means to said valve device.
 10. A mixing and kneading device as setforth in claim 9, wherein said valve device comprises a valve casing,supply, exhaust and motor ports in said valve casing, a slidable, hollowpiston type valve member having flow passages therein in said casing forselectively interconnecting said supply and exhaust ports to said motorports to supply and exhaust pressure fluid to and from saiD cylinder.11. A mixing and kneading device as set forth in claim 10, a flowregulating valve member located within said hollow valve member tocooperate with said flow passages to control the flow of fluidtherethrough, and means responsive to the reciprocatory movements ofsaid shaft to actuate said regulating valve to a position wherein itcooperates with said flow passages to regulate the flow of pressurefluid therethrough, said means responsive to the reciprocatory movementspositioning said regulating valve in its flow regulating positions atthe end positions of the shaft strokes.
 12. A mixing and kneading deviceas set forth in claim 1, wherein the vanes are secured to the shaft indiametrically opposed pairs for an additional wall scraping function,and cooperate with their corresponding stationary elements.
 13. A mixingand kneading device as set forth in claim 1, wherein said housing isprovided with a connection adapted to be connected to a vacuum means.14. A mixing and kneading device as set forth in claim 1, wherein thereciprocating means is a stationary pressure fluid motor comprisingrelatively movable piston and cylinder elements with one of the elementsconnected to said shaft, and wherein the rotary means comprises avariable speed motor mounted upon said shaft for movement therewith. 15.A mixing and kneading device as set forth in claim 14, wherein saidrotary means is housed in a case, said case being mounted on a pivotablesupport.
 16. A mixing and kneading device as claimed in claim 15,wherein said pressure fluid motor is in axial alignment with the end ofsaid shaft and said variable speed rotary motor is connected to saidshaft by gear means concentric with said shaft.